Intracellular calcium concentrations are regulated by a family of inositol phosphates, which act as second messengers in the calcium cell signaling pathway. ITPK1 (inositol 1,3,4-triphosphate 5/6 kinase), also known as ITRPK1, is a 414 amino acid monomer that belongs to the ITPK1 family and exists as two alternatively spliced isoforms. Widely expressed, ITPK1 is found at highest levels in brain, followed by heart, skeletal muscle, kidney, pancreas, liver, placenta and lung. ITPK1 contains one ATP-grasp domain and has been found to phosphorylate various.